Radiation detecting apparatus

ABSTRACT

A radiation detecting apparatus includes a radiation detector including a scintillator for converting radiation that has passed through a subject into visible light, and a substantially rectangular shaped photoelectric transducer board for converting the visible light into radiographic image information, and a casing housing the radiation detector therein. The casing is of a substantially rectangular shape and includes an upper plate, a lower plate, and a frame interconnecting the upper plate and the lower plate. The frame has a recess defined therein, which faces and is spaced from a corner of the photoelectric transducer board, the recess being concave in a direction away from the corner.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/441,454, filed Apr. 6, 2012, which is based upon and claims thebenefit of priority from Japanese Patent Application No. 2011-085292filed on Apr. 7, 2011, the content of each of which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiation detecting apparatusincluding a radiation conversion panel housed in a casing.

2. Description of the Related Art

In the medical field, there have widely been employed radiographic imagecapturing apparatus that apply a radiation to a subject and guideradiation that has passed through the subject to a radiation detector,which captures radiographic image information of the subject from theradiation. Known forms of radiation detectors include a conventionalradiation film for recording radiographic image information by way ofexposure, and a stimulable phosphor panel for storing radiation energyrepresenting radiographic image information in a phosphor, andreproducing the radiographic image information as stimulated light byapplying stimulating light to the phosphor. The radiation film with therecorded radiographic image information is supplied to a developingdevice to develop the radiographic image information, or alternatively,the stimulable phosphor panel is supplied to a reading device, whichreads a visible image from the radiographic image information.

Radiation detecting apparatus are widely used in operating theaters ofhospitals to provide surgeons with medical imaging information. Inoperating theaters, it is often necessary to read recorded radiographicimage information from a radiation detecting apparatus immediately aftersuch radiographic image information has been captured, for the purposeof quickly and appropriately treating the patient. To meet such arequirement, there have been developed radiation detecting apparatus,which convert radiation directly into an electric signal, or whichincorporate a photoelectric transducer board for converting radiationinto visible light with a scintillator and then converting the visiblelight into an electric signal (see, for example, Japanese Laid-OpenPatent Publication No. 2009-257914, Japanese Laid-Open PatentPublication No. 2010-197404, Japanese Laid-Open Patent Publication No.2010-160044, Japanese Laid-Open Patent Publication No. 2007-300996, andJapanese Laid-Open Patent Publication No. 2003-185753).

SUMMARY OF THE INVENTION

While the radiation detecting apparatus is carried from place to place,the radiation detecting apparatus may accidentally be dropped onto thefloor or be touched or hit by another object. In the event of such anaccident, at least the photoelectric transducer board tends to contact aside wall of a casing of the radiation detecting apparatus, and to havea corner thereof deformed or damaged under the overall weight of thephotoelectric transducer board, if the corner is in a lowermost positionwhen the radiation detecting apparatus is dropped onto the floor, or ifthe corner is located near the object when the radiation detectingapparatus is touched or hit by the object. The radiation detectingapparatus disclosed in the above publications do not incorporatestructures therein for protection against risks of accidental damage.

It is an object of the present invention to provide a radiationdetecting apparatus, which keeps casing side walls mechanically strongand prevents a photoelectric transducer board, e.g., corners thereof,from becoming damaged, thereby enabling increased operationalreliability during use, even if the radiation detecting apparatus isaccidentally dropped onto the floor or is touched or hit by anotherobject while the radiation detecting apparatus is carried.

According to the present invention, there is provided a radiationdetecting apparatus comprising a radiation detector including ascintillator for converting radiation that has passed through a subjectinto visible light, and a substantially cuboid shaped photoelectrictransducer board for converting the visible light into radiographicimage information. The radiation detecting apparatus further comprises acasing housing the radiation detector therein, wherein the casing is ofa substantially cuboid shape and includes an upper plate, a lower plate,and a side plate interconnecting the upper plate and the lower plate.The side plate has a recess defined therein, which faces toward and isspaced from a corner of the photoelectric transducer board, the recessbeing concave in a direction away from the corner.

More specifically, the recess is defined in a corner on the innerperipheral edge of the side plate in facing relation to the corner ofthe photoelectric transducer board. Therefore, a sufficient mechanicalstrength of the side plate, which is required to connect the upper plateand the lower plate, is not lowered.

Since the recess is concave in the direction away from the corner of thephotoelectric transducer board, even if the radiation detectingapparatus is dropped by mistake onto the floor or is touched or hit byanother object while the radiation detecting apparatus is being carried,only the sides of the photoelectric transducer board are likely tocontact the sides, i.e., the inner wall surfaces, of the side plate,whereas the corner of the photoelectric transducer board does not comeinto contact with or impinge on the frame. Even if some of the sides ofthe photoelectric transducer board are brought into contact with some ofthe inner wall surfaces of the side plate, the photoelectric transducerboard is supported simultaneously by two of the inner wall surfaces, andhence the overall weight of the photoelectric transducer board is notconcentrated on a local region of the side plate. Consequently, thephotoelectric transducer board is free of risks of damage caused by thesides, i.e., the inner wall surfaces, of the side member.

According to the present invention, as described above, even if theradiation detecting apparatus is dropped by mistake onto the floor or istouched or hit by another object while the radiation detecting apparatusis being carried, the photoelectric transducer board, e.g., cornersthereof, are prevented from becoming damaged, and the mechanicalstrength of the side plate of the casing is maintained. Therefore,reliability of the radiation detecting apparatus during use isincreased.

The recess may comprise a cavity, which is concave as viewed in plan. Ifthe corner of the photoelectric transducer board is displaced toward thecavity in order to bring two adjacent sides of the photoelectrictransducer board into contact with respective inner wall surfaces of theside plate on both sides of the cavity, then the corner between the twoadjacent sides is spaced from a bottom of the cavity by a minimumdistance in a range from 1 mm to 5 mm.

Even if the sides of the photoelectric transducer board come intocontact with the inner wall surfaces of the side plate, a gap remainsbetween the corner of the photoelectric transducer board and the cavity.Thus, even if the corner of the photoelectric transducer board vibratesdue to an impact that may occur if the radiation detecting apparatus isdropped onto the floor or is touched or hit by another object, thecorner is not brought into contact with the bottom surface or inner wallsurfaces of the cavity, and hence the photoelectric transducer board isprevented from becoming damaged upon vibration thereof.

The cavity may be defined by two side wall surfaces adjoining therespective inner wall surfaces, and a bottom surface interconnecting thetwo side wall surfaces. The corner and the bottom surface of the cavitymay be spaced from each other by the minimum distance in the range from1 mm to 5 mm.

The corner may have a single apex, and the single apex of the corner andthe bottom surface of the cavity may be spaced from each other by theminimum distance in the range from 1 mm to 5 mm.

Alternatively, the corner may have at least two apexes, and one of theat least two apexes, which is closest to the bottom surface of thecavity, and the bottom surface may be spaced from each other by theminimum distance in the range from 1 mm to 5 mm.

The recess may comprise a cavity, which is concave as viewed in plan,and which also is concave as viewed in vertical cross section. Thecavity may be defined between a first surface, which is closer to theupper plate, and a second surface, which is closer to the lower plate.The photoelectric transducer board may have a surface facing the upperplate and spaced from the first surface by a minimum distance, and asurface facing the lower plate and spaced from the second surface by aminimum distance, each of the minimum distances being in the range from1 mm to 5 mm.

Accordingly, even if the sides of the photoelectric transducer boardcontact the inner wall surfaces of the side plate, a gap remains betweenthe corner of the photoelectric transducer board and the cavity, e.g.,the bottom surface thereof. In addition, a gap remains between thesurface of the photoelectric transducer board that faces toward theupper plate and the first surface, and a gap also remains between thesurface of the photoelectric transducer board that faces toward thelower plate and the second surface. Even if the corner of thephotoelectric transducer board vibrates in directions across a planethereof, due to an impact that may occur if the radiation detectingapparatus is dropped onto the floor or is touched or hit by anotherobject, the corner is prevented from coming into contact with inner wallsurfaces of the cavity, i.e., the bottom surface, the first surface, thesecond surface, etc., and hence the photoelectric transducer board isprevented from becoming damaged due to vibrations.

The radiation detecting apparatus may further comprise a first baseplate disposed between the upper plate and the photoelectric transducerboard and supporting the radiation detector thereon. The scintillatormay be disposed on a surface of the photoelectric transducer board,which is remote from the first base plate. The first base plate has athickness ta, the photoelectric transducer board has a thickness tb, thescintillator has a thickness tc, and the cavity has a height ha along athickness direction of the photoelectric transducer board, wherein thethicknesses ta, tb, tc, and the height ha are related to each other bythe inequality tb<ha<(ta+tb+tc).

More specifically, the height of the cavity is greater than thethickness of the photoelectric transducer board, but is smaller than thesum of the thicknesses of the first base plate, the photoelectrictransducer board, and the scintillator. Because of the above-describedthickness relationship and also due to the gaps referred to above, ifthe photoelectric transducer board is displaced upon the radiationdetecting apparatus being dropped onto the floor or touched or hit byanother object, the corner of the photoelectric transducer boardpartially enters into the cavity, but is prevented from coming intocontact or colliding with the side plate.

The photoelectric transducer board may have a transverse length, whichis greater than a transverse length of the scintillator, and alongitudinal length, which is greater than a longitudinal length of thescintillator. Therefore, even if the photoelectric transducer board isdisplaced together with the scintillator if the radiation detectingapparatus is dropped onto the floor or is touched or hit by anotherobject, the scintillator is prevented from coming into contact orcolliding with the side plate.

The upper plate and the first base plate may be fixed to each other byan adhesive layer, and the first base plate and the photoelectrictransducer board may be bonded to each other by a pressure-sensitiveadhesive. Since the first base plate and the photoelectric transducerboard are bonded to each other by the pressure-sensitive adhesive tape,the radiation detector can easily be replaced or repaired. Such astructure makes it easier for the photoelectric transducer board to moveif the radiation detecting apparatus is dropped onto the floor or istouched or hit by another object. However, as described above, even ifthe photoelectric transducer board is displaced, the corner of thephotoelectric transducer board partially enters into the cavity, whilebeing prevented from coming into contact or colliding with the sideplate. Therefore, even though the above structure allows the radiationdetector to easily be replaced or repaired, reliability of the radiationdetecting apparatus during use can be increased.

The radiation detecting apparatus may further comprise a second baseplate disposed between the scintillator and the lower plate, and whichsupports the radiation detector thereon in coaction with the first baseplate. The upper plate and the first base plate may be fixed to eachother by an adhesive layer. The first base plate and the photoelectrictransducer board may be bonded to each other by a pressure-sensitiveadhesive. The second base plate and the scintillator may also be bondedto each other by a pressure-sensitive adhesive. Such a structure allowsthe radiation detector to easily be replaced or repaired, while alsoincreasing reliability of the radiation detecting apparatus during use.

The first base plate preferably is made of a non-metal material, and thesecond base plate preferably is made principally from a non-metalmaterial. Such non-metal materials enable the radiation detectingapparatus to be made lighter in weight.

According to the present invention, as described above, even if theradiation detecting apparatus is dropped onto the floor by mistake, oris touched or hit by another object while the radiation detectingapparatus is being carried, the photoelectric transducer board, e.g., acorner thereof, is prevented from being damaged, while at the same time,the mechanical strength of the side plate of the casing is maintained.Therefore, reliability of the radiation detecting apparatus during usecan be increased.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view, partially in block form, of a radiographicimage capturing system, which incorporates therein a radiation detectingapparatus according to an embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view taken along line II-II ofFIG. 3, showing structural details of the radiation detecting apparatus;

FIG. 3 is an enlarged cross-sectional view taken along line of FIG. 2;

FIGS. 4A and 4B are enlarged cross-sectional views each showing apositional relationship between a corner of a photoelectric transducerboard and a recess defined in a frame;

FIG. 5 is an enlarged fragmentary cross-sectional view of the radiationdetecting apparatus;

FIG. 6 is a circuit diagram, partially in block form, of the radiationdetecting apparatus;

FIG. 7 is a block diagram of the radiation detecting apparatus;

FIG. 8 is a view showing areas of a second member of a second substrateonto which circuit boards are projected;

FIGS. 9A through 9D are fragmentary cross-sectional views showing anexample of a process for fabricating the second member of the secondsubstrate;

FIG. 10 is an enlarged cross-sectional view, partially omitted fromillustration, of a modified radiation detector according to amodification of the present invention; and

FIG. 11 is an enlarged cross-sectional view, partially omitted fromillustration, of a signal output unit of the modified radiationdetector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Radiation detecting apparatus according to embodiments of the presentinvention will be described in detail below with reference to FIGS. 1through 11. Various numerical ranges, which are referred to in thefollowing description, should be interpreted as including numericalvalues at ends of the ranges as upper and lower limit values thereof.

As shown in FIG. 1, a radiographic image capturing system 10 accordingto an embodiment of the present invention includes a radiation source 16for applying a dose of radiation 12 to a subject 14 according to givenimage capturing conditions, a radiation detecting apparatus 20 fordetecting radiation 12 that has passed through the subject 14, a displaydevice 22 for displaying a radiographic image based on radiation 12 thatis detected by the radiation detecting apparatus 20, and a console(controller) 24 for controlling the radiation source 16, the radiationdetecting apparatus 20, and the display device 22. The console 24, theradiation source 16, the radiation detecting apparatus 20, and thedisplay device 22 exchange signals via wireless communication, forexample.

The console 24 is connected to a radiology information system (RIS) 26,which generally manages radiographic image information as well as otherinformation handled by the radiological department of a hospital inwhich the radiographic image capturing system 10 is installed. The RIS26 is connected to a hospital information system (HIS) 28, whichgenerally manages medical information in the hospital.

As shown in FIG. 2, the radiation detecting apparatus 20 includes asubstantially cuboid casing 30 made of a material that is permeable toradiation 12. The casing 30 has a substantially planar first plate(upper plate) 34 providing an outer front surface (irradiated surface)32 that is exposed to radiation 12, a frame (side plate) 36 providingside surfaces, a substantially planar second plate (lower plate) 40providing an outer rear surface 38 remote from the front surface 32, anda chassis 46 attached to the frame 36 and disposed between the firstplate 34 and the second plate 40, thereby dividing a storage space inthe casing 30 into a first compartment 42 near the first plate 34 and asecond compartment 44 near the second plate 40.

The frame 36 has an annular groove 48 defined in an inner wall thereofnear the front surface 32 for receiving a peripheral edge of the firstplate 34 fitted therein. The frame 36 also has an annular flat step 50on an inner wall thereof substantially at a central position along theheight or width of the frame 36. The chassis 46 has a peripheral edge,which is fastened by screws or an adhesive to the annular flat step 50.A joint 52, which is in the form of a plurality of joint members eachhaving an L-shaped cross section or a single frame member having anL-shaped cross section, is fixed to the peripheral edge of the chassis46 near the rear surface 38. The second plate 40 is joined to the joint52. The joint 52, the peripheral edge of the chassis 46, and the flatstep 50 of the frame 36 may be secured together by screws, for example.One or more circuit boards 56 having various electronic components 54mounted thereon are disposed on a surface of the chassis 46 that facesthe rear surface 38. The second plate 40 has an inner surface includinga portion held against a portion of the joint 52, and which is fastenedthereto by screws or an adhesive. A plurality of spacers 58 are disposedbetween and joined to the chassis 46 and the second plate 40. Thespacers 58 provide a space or height between the chassis 46 and thesecond plate 40, which is large enough to house at least the circuitboards 56 in the second compartment 44. The spacers 58 also preserve theflatness of at least a central region of the second plate 40, which ispositioned inwardly of the portion of the second plate 40 that isfastened to the joint 52.

A radiation detector 60 is disposed in the first compartment 42, whichis surrounded by the first plate 34, the frame 36, and the chassis 46.More specifically, a first base plate 62, which supports the radiationdetector 60 thereon, is fixed by a first adhesive layer 64 to an innersurface of the first plate 34, which faces away from the front surface32 (see FIG. 5). A second base plate 66, which supports the radiationdetector 60 thereon and which also reinforces the scintillator 78, isfixed by a second adhesive layer 68 to a surface of the chassis 46,which faces toward the first plate 34 (see FIG. 5). The radiationdetector 60 is disposed between the first base plate 62 and the secondbase plate 66. The first base plate 62 has a thickness in a range up to0.5 mm, whereas the second base plate 66 has a thickness in a range from0.8 mm to 1.5 mm.

The radiation detector 60 converts radiation 12 that has passed throughthe subject 14 into radiographic image information, and outputs theradiographic image information as an analog electric signal to theconsole 24. The radiation detecting apparatus 20 also includes a battery70, a cassette controller 72, and a transceiver 74 (see FIG. 6), inaddition to the circuit boards 56 and the radiation detector 60. Thebattery 70, which serves as a power supply for the radiation detectingapparatus 20, supplies electric power to the radiation detector 60, thecassette controller 72, and the transceiver 74. The cassette controller72 controls the radiation detector 60 upon electric power being suppliedthereto from the battery 70. The transceiver 74 exchanges signals withthe console 24, such signals being representative of information(radiographic image information) of radiation 12 detected by theradiation detector 60.

As shown in FIGS. 2 and 5, the radiation detector 60 includes asubstantially cuboid photoelectric transducer board 76 disposed closerto the front surface 32, and a scintillator 78 disposed closer to therear surface 38. The scintillator 78 is made of a phosphor having amatrix of GOS (Gd₂O₂S:Tb), CsI:Tl, or the like, which converts radiation12 that has passed through the subject 14 into visible light. Thephotoelectric transducer board 76 includes a photoelectric transducerlayer 84 (see FIG. 6) for converting visible light from the scintillator78 into an electric signal. The photoelectric transducer layer 84includes an array of thin-film transistors 80 (see FIG. 6, hereinafterreferred to as “TFTs 80”), and an array of solid-state detectingelements 82 (see FIG. 6, hereinafter also referred to as “pixels 82”)made of amorphous silicon (a-Si) or the like.

Planar configurations of the frame 36, the photoelectric transducerboard 76, etc., will be described below with reference to FIGS. 3, 4Aand 4B.

As shown in FIG. 3, the frame 36 has recesses 200 defined therein, whichface toward and are spaced from respective corners 76 a of thephotoelectric transducer board 76. More specifically, the recesses 200are defined in respective corners 36 a on an inner peripheral edge ofthe frame 36, in facing relation to the respective corners 76 a of thephotoelectric transducer board 76.

Each of the recesses 200 is in the form of a cavity 202, which isconcave both as viewed in plan and in vertical cross section. Asindicated by the two-dot-and-dash lines in FIG. 4A, if the correspondingcorner 76 a of the photoelectric transducer board 76 were displacedtoward the cavity 202 in order to bring two adjacent sides 76 b of thephotoelectric transducer board 76 into contact with respective innerwall surfaces 36 b of the frame 36 on both sides of the cavity 202, thenthe corner 76 a between the sides 76 b would be spaced from the bottomof the cavity 202 by a minimum distance da in a range from 1 mm to 5 mm.More specifically, the cavity 202 is defined by two side wall surfaces202 a adjoining the respective inner wall surfaces 36 b, and a bottomsurface 202 b interconnecting the side wall surfaces 202 a. The corner76 a of the photoelectric transducer board 76 and the bottom surface 202b of the cavity 202 are spaced from each other by the minimum distanceda in the range from 1 mm to 5 mm. More specifically, as shown in FIG.4A, the corner 76 a of the photoelectric transducer board 76 has an apex76 t, which is spaced from the bottom surface 202 b of the cavity 202 bythe minimum distance da in the range from 1 mm to 5 mm. Alternatively,as shown in FIG. 4B, the corner 76 a of the photoelectric transducerboard 76 may have two or more apexes 76 t, wherein one of the apexes 76t, which is closest to the bottom surface 202 b of the cavity 202, isspaced from the bottom surface 202 b by the minimum distance da in therange from 1 mm to 5 mm.

As shown in FIG. 2, the cavity 202 is defined between a first surface202 c, which is disposed closer to the first plate 34, and a secondsurface 202 d, which is disposed closer to the second plate 40. Thephotoelectric transducer board 76 has a surface 76 c facing toward thefirst plate 34 and which is spaced from the first surface 202 c by aminimum distance d1, and another surface 76 d facing toward the secondplate 40 and which is spaced from the second surface 202 d by a minimumdistance d2. Each of the minimum distances d1, d2 is in a range from 1mm to 5 mm.

If the thickness of the first base plate 62 is represented by ta, thethickness of the photoelectric transducer board 76 is represented by tb,the thickness of the scintillator 78 is represented by tc, and theheight of the cavity 202 along the thickness direction of thephotoelectric transducer board 76 is represented by ha, then thedimensions are related to each other by the inequality tb<ha<(ta+tb+tc).

As shown in FIG. 3, the photoelectric transducer board 76 has a verticalor transverse length La, which is greater than the vertical ortransverse length Lb of the scintillator 78. The photoelectrictransducer board 76 also has a horizontal or longitudinal length Lc,which is greater than the horizontal or longitudinal length Ld of thescintillator 78.

As shown in FIG. 5, the scintillator 78 and the photoelectric transducerboard 76 are joined to each other with an intermediate layer 86interposed therebetween. The intermediate layer 86 has a thickness in arange from 10 μm to 50 μm, and a haze level in the range from 3% to 50%.The intermediate layer 86 should preferably be made of an adhesivecontaining a filler. The adhesive preferably is a hot-melt adhesive, areactive hot-melt adhesive, or a thermosetting adhesive. A hot-meltadhesive is particularly preferable, in that such a hot-melt adhesivecan level out surface irregularities of the photoelectric transducerboard 76.

The filler may be an inorganic material such as alumina, silica,titanium oxide, zirconium oxide, yttrium oxide, or the like, or anorganic material such as highly cross-linked acrylic resin, highlycross-linked polystyrene, melamine-formaldehyde resin, silicone resin,or the like. Such filler materials may be used alone or in combination.

The intermediate layer 86 is not limited to the above adhesives, but maybe a pressure-sensitive adhesive, such as a polyacrylicpressure-sensitive adhesive, a silicone rubber pressure-sensitiveadhesive, a polyvinyl butyl ether pressure-sensitive adhesive, apolyisobutylene pressure-sensitive adhesive, a natural rubberpressure-sensitive adhesive, or the like. Such a pressure-sensitiveadhesive can be peeled off from a surface after having been bonded tothe surface.

Between the scintillator 78 and the second base plate 66, there aredisposed a light reflecting layer 88 for reflecting light, an antistaticelectrically conductive layer 90, and a support layer 92, which arearranged in this order from the scintillator 78 toward the second baseplate 66. The photoelectric transducer board 76, the scintillator 78,the light reflecting layer 88, the electrically conductive layer 90, andthe support layer 92 are integrally combined with each other by anultraviolet-curable adhesive 93.

The support layer 92, which may comprise a plastic substrate, a siliconsubstrate, a carbon substrate, or the like, has a thickness in a rangefrom 0.15 mm to 0.30 mm. The support layer 92 may be made of a whiteresin material, which is produced by mixing a resin material such aspolyethylene terephthalate (PET), polycarbonate, polyethylenenaphthalate, or the like, with a pigment of titanium oxide, aluminumoxide, or the like, or any of various types of metal particles or metalfoils.

The electrically conductive layer 90 preferably is made of a metalmaterial, a metal oxide material, or an electrically conductive organicmaterial. The electrically conductive layer 90 has a thickness of 5 μmor smaller. The metal material should be magnesium, magnesium alloy,aluminum alloy, or the like, as such materials possess low radiationabsorptance. The metal oxide material preferably is composed of acicularmicroparticles of SnO₂ (Sb-doped). The electrically conductive organicmaterial preferably is an electrically conductive carbon film or thelike.

The light reflecting layer 88 is a layer containing a light reflectingmaterial. Examples of suitable light reflecting materials include whitepigments of Al₂O₃, ZrO₂, MgO, BaSO₄, SiO₂, ZnS, ZnO, CaCO₃, Sb₂O₃,Nb₂O₅, 2PbCO₃.Pb(OH)₂, PbF₂, BiF₃, Y₂O₃, YOCl, MIIFX (where MII refersto at least one of Ba, Sr, and Ca, and X refers to at least one of Cland Br), lithopone (BaSO₄+ZnS), magnesium silicate, basic silicatesulfate, basic phosphate, and aluminum silicate; various types of metalparticles or metal foils; and hollow polymer particles. The abovematerials may be used alone or in combination. Among the abovematerials, Al₂O₃, ZrO₂, PbF₂, BiF₃, Y₂O₃, and YOCl are particularlypreferable, due to the higher refractive indices exhibited thereby. Thelight reflecting layer 88 has a thickness in a range from 50 μm to 80μm.

The support layer 92 and the second base plate 66 are bonded to eachother by a non-illustrated double-sided pressure-sensitive adhesivetape. Similarly, the photoelectric transducer board 76 and the firstbase plate 62 are bonded to each other by a non-illustrated double-sidedpressure-sensitive adhesive tape. The double-sided pressure-sensitiveadhesive tapes include a pressure-sensitive adhesive that can be peeledoff from a surface after it has been bonded to the surface. Therefore,the radiation detector 60 can easily be detached from the radiationdetecting apparatus 20, so as to enable repairs to be performed thereon.However, the support layer 92 and the second base plate 66 may be bondedsecurely to each other by an adhesive. Similarly, the photoelectrictransducer board 76 and the first base plate 62 may be bonded securelyto each other by an adhesive.

In the present embodiment, the radiation detector 60 is a face-sidereadout ISS (Irradiation Side Sampling) type of radiation detector,including the photoelectric transducer board 76 and the scintillator 78,which are arranged successively along the direction in which radiation12 is applied, wherein the photoelectric transducer board 76 closer tothe first plate 34 converts light emitted from the scintillator 78 intoelectric charges in order to read radiographic image information.However, the radiation detector 60 may also be a reverse-side readoutPSS (Penetration Side Sampling) type of radiation detector, in which thephotoelectric transducer board 76 positioned behind the scintillator 78converts light emitted from the scintillator 78 into electric charges inorder to read radiographic image information.

The scintillator 78 normally emits more intensive light from the frontsurface thereof, which is irradiated with radiation 12, than from therear surface thereof. A face-side readout type radiation detector 60according to the present embodiment allows light emitted from thescintillator 78 to reach the photoelectric transducer board 76, i.e.,the photoelectric transducer layer 84, in a shorter period of time thana reverse-side readout type radiation detector 60. Further, since lightemitted from the scintillator 78 is prevented from being scattered andattenuated more effectively, the resolution of the produced radiographicimage information is increased.

Circuit details of the radiation detecting apparatus 20 will bedescribed below with reference to FIGS. 6 and 7.

As shown in FIG. 6, the radiation detecting apparatus 20 comprises anarray of TFTs 80 arranged in rows and columns, and a photoelectrictransducer layer 84 including pixels 82, and made of a material such asa-Si or the like for converting visible light into electric signals. Thephotoelectric transducer layer 84 is disposed on the array of TFTs 80.In a case where radiation is applied to the radiation detectingapparatus 20, the pixels 82 generate electric charges by convertingvisible light into analog electric signals, which are stored therein asgenerated electric charges. Then, in a case where the TFTs 80 are turnedon along each row at a time, the stored electric charges are read fromthe pixels 82 as an image signal.

The TFTs 80 are connected respectively to the pixels 82. Gate lines 94,which extend parallel to the rows, and signal lines 96, which extendparallel to the columns, are connected to the TFTs 80. The gate lines 94are connected to a line scanning driver 98, and the signal lines 96 areconnected to a multiplexer 100. The gate lines 94 are supplied withcontrol signals Von, Voff for turning on and off the TFTs 80 along therows from the line scanning driver 98. The line scanning driver 98includes a plurality of switches SW1 for switching between the gatelines 94, and an address decoder 102 for outputting a selection signalfor selecting one of the switches SW1 at a time. The address decoder 102is supplied with an address signal from the cassette controller 72.

The signal lines 96 are supplied with electric charges stored in thepixels 82 through the TFTs 80 arranged in the columns. The electriccharges supplied to the signal lines 96 are amplified by amplifiers 104,which are connected respectively to the signal lines 96. The amplifiers104 are connected through respective sample and hold circuits 106 to themultiplexer 100. The multiplexer 100 includes a plurality of switchesSW2 for successively switching between the signal lines 96, and anaddress decoder 108 for outputting a selection signal for selecting oneof the switches SW2 at a time. The address decoder 108 is supplied withan address signal from the cassette controller 72. The multiplexer 100has an output terminal connected to an A/D converter 110. A radiographicimage signal, which is generated by the multiplexer 100 based on theelectric charges from the sample and hold circuits 106, is converted bythe A/D converter 110 into a digital image signal representingradiographic image information, which is supplied to the cassettecontroller 72.

In FIG. 6, the line scanning driver 98, the multiplexer 100, theamplifiers 104, the sample and hold circuits 106, and the A/D converter110 are included in the electronic components 54. Portions of the gatelines 94, which extend from the line scanning driver 98 to thephotoelectric transducer layer 84, as well as portions of the signallines 96, which extend from the photoelectric transducer layer 84 to theamplifiers 104, are included in the photoelectric transducer board 76.

The TFTs 80, which function as switching devices, may be combined withanother image capturing device such as a CMOS (Complementary Metal-OxideSemiconductor) image sensor or the like. Alternatively, the TFTs 80 maybe replaced with a CCD (Charge-Coupled Device) image sensor for shiftingand transferring electric charges with shift pulses, which correspond togate signals in the TFTs.

As shown in FIG. 7, the cassette controller 72 of the radiationdetecting apparatus 20 includes an address signal generator 112, animage memory 114, and a cassette ID memory 116.

The address signal generator 112 supplies address signals to the addressdecoder 102 of the line scanning driver 98 and to the address decoder108 of the multiplexer 100 shown in FIG. 6. The image memory 114 storesradiographic image information detected by the radiation detector 60.The cassette ID memory 116 stores cassette ID information foridentifying the radiation detecting apparatus 20.

The transceiver 74 sends the cassette ID information, which is stored inthe cassette ID memory 116, and the radiographic image information,which is stored in the image memory 114, to the console 24 via awireless communication link.

The first base plate 62 is made of a material having a specific gravityof 2.8 or smaller for reducing the overall weight of the radiationdetecting apparatus 20. The material of the first base plate 62 is anyone of a composite material including carbon fibers, cellulose fibers,glass fibers, engineering plastics, and biomass plastics.

As shown in FIG. 5, the second base plate 66 comprises two first members118 and a second member 120, which have different functionsrespectively. As with the first base plate 62, each of the first members118 is made of a material having a specific gravity of 2.8 or smallerfor reducing the overall weight of the radiation detecting apparatus 20.The material of the first members 118 is any one of a composite materialincluding carbon fibers, cellulose fibers, glass fibers, engineeringplastics, and biomass plastics. The second member 120 is made of a metalmaterial for attenuating scattered rays from radiation 12 that passesthrough the casing 30, e.g., scattered rays from behind the second baseplate 66. As shown in FIG. 5, the second member 120 is sandwichedbetween and integrally combined with the first members 118.

The first base plate 62 and the first members 118 of the second baseplate 66 may be made of the same material or different materials.

The aforementioned composite material containing carbon fibers is acarbon-fiber-reinforced plastic (CFRP), a composite material of asandwiched structure having a preform of carbon fibers encased in afoaming material and then impregnated with a resin, or a compositematerial of CFRP coated with a foaming material. The aforementionedcomposite material containing cellulose fibers is a composite materialcontaining cellulose microfibril fibers. The aforementioned compositematerial containing glass fibers is a glass-fiber-reinforced plastic(GFRP).

The first base plate 62 preferably is made of highly rigid carbon of PAN(polyacrylonitrile) carbon fibers, the thermal conductivity of which isrelatively low, in order to prevent the subject (patient) 14 fromfeeling heat through the first base plate 62 in a case where theelectronic components 54, etc., of the radiation detecting apparatus 20are heated. The first members 118 of the second base plate 66 preferablyare made of highly rigid carbon made up of pitch-based carbon fibers,the thermal conductivity of which is higher than the PAN carbon fibers,in order to effectively radiate heat outwardly from the radiationdetecting apparatus 20 through the chassis 46.

The engineering plastics include polyamide (PA), polyacetal (POM),polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE),polybutylene terephthalate (PBT), polyethylene terephthalate (PET),glass-fiber-reinforced polyethylene terephthalate (GF-PET), ultra highmolecular weight polyethylene (UHPE), syndiotactic polystyrene (SPS),cyclic polyolefin (COP), polyphenylene sulfide (PPS), polysulfone (PSF),amorphous polyarylate (PAR), polyether sulfone (PES), liquid crystalpolyester (LCP), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), epoxy (EP), etc.

If the thickness of the second member 120 of the second base plate 66 isconstant, then the attenuation distribution of scattered rays frombehind becomes irregular. More specifically, since scattered rays frombehind are attenuated by metal layers of the electrically conductivepattern of the circuit boards 56, areas of the second member 120, whichare aligned with the circuit boards 56, and other areas of the secondmember 120 attenuate the scattered rays to different degrees. As aresult, noise images produced by attenuated scattered rays, which areapplied to the scintillator 78, correspond to profiles of the circuitboards 56, and hence are easy to notice and tend to make the capturedradiographic image lower in quality. Such problems do not arise if thesecond member 120 is capable of absorbing all of the scattered rays.However, in this case, the second base plate 66 would have to be made ofa heavy material such as lead or the like, and thus, depending on thesize of the second base plate 66, the radiation detecting apparatus 20could not be reduced in weight.

According to the present embodiment, the thickness of the second member120 of the second base plate 66 is changed at locations where thecircuit boards 56 are positioned. For example, as shown in FIG. 8, thesecond member 120 has areas Za toward which the circuit boards 56project, and such areas Za have a smaller thickness than other areas ofthe circuit board 56.

The metal material of the second member 120 of the second base plate 66may be aluminum, silver, copper, or the like, and preferably is the sameas the metal material of the electrically conductive pattern of thecircuit boards 56. For example, since the electrically conductivepattern of the circuit boards 56 is produced by selectively etching acopper foil, the metal material of the second member 120 of the secondbase plate 66 preferably is copper.

The areas Za of the second member 120 preferably are thinner than otherareas of the circuit board 56 by an amount equal to the thickness of theelectrically conductive pattern of the circuit boards 56. If each of thecircuit boards 56 comprises a stacked assembly of electricallyconductive patterns, then the areas Za of the second member 120 shouldpreferably be thinner than other areas of the circuit board 56 by anamount equal to the thickness of the stacked assembly of electricallyconductive patterns.

Since the thickness of the areas Za of the second member 120, whichcorrespond to the circuit boards 56, is reduced, the attenuationdistribution of scattered rays from behind is made uniform over theentirety of the second member 120. Accordingly, noise images produced byattenuated scattered rays that are applied to the scintillator 78 are ofa constant level as a whole, and hence are not easy to notice. Further,since the noise images are constant in level, the noise images caneasily be removed by subsequent simple image processing, such as anoffsetting process.

A process of fabricating the second base plate 66 will be describedbelow with reference to FIGS. 9A through 9D. A first stacked assembly124 a (see FIG. 9A) comprises a plurality of preforms 122 made of carbonfibers. A second member 120 in the form of a metal foil, a metal film, ametal sheet, or the like is placed on the first stacked assembly 124 a(see FIG. 9B). A preform 122 of carbon fibers is placed on a thinnerportion 120 a of the second member 120, thereby making the upper surfaceof the second member 120 flat (see FIG. 9C). Then, a second stackedassembly 124 b, which comprises a plurality of preforms 122 made ofcarbon fibers, is placed on the second member 120 (see FIG. 9D).Thereafter, the first stacked assembly 124 a, the second member 120, andthe second stacked assembly 124 b are heated and pressurized (see FIG.9D), thereby producing the second base plate 66.

As shown in FIG. 2, the first plate 34 of the casing 30 may be made ofthe same material as the first base plate 62, and the second plate 40 ofthe casing 30 may be made of the same material as the first member 118of the second base plate 66. The chassis 46 may be made of a materialhaving a specific gravity of 2.8 or smaller, for thereby reducing theoverall weight of the radiation detecting apparatus 20. Morespecifically, the material of the chassis 46 may be a metal materialsuch as aluminum, aluminum alloy, magnesium, magnesium alloy, or thelike.

The frame 36 of the casing 30 may be made of a synthetic resin or thelike in order to enable the radiation detector 60 to be repaired,serviced, or replaced with ease. More specifically, the frame 36 can beelastically deformed to allow the first plate 34 and the first baseplate 62 to easily be removed from the frame 36, while also enabling theradiation detector 60 to be removed with ease. The frame 36 can also beelastically deformed to facilitate installation of such components.

According to the present embodiment, as shown in FIGS. 3, 4A and 4B, theframe 36 has recesses 200 defined in portions thereof that face towardrespective corners 76 a of the photoelectric transducer board 76, therecesses 200 being concave in directions away from the corners 76 a.More specifically, the recesses 200 are defined in respective corners 36a on the inner peripheral edge of the frame 36, in facing relation tothe respective corners 76 a of the photoelectric transducer board 76.Therefore, the mechanical strength of the frame 36, which is required toconnect the first plate 34 and the second plate 40, is not lowered.Since the recesses 200 are concave in directions away from the corners76 a of the photoelectric transducer board 76, even if the radiationdetecting apparatus 20 is dropped by mistake onto the floor, or istouched or hit by another object while the radiation detecting apparatus20 is being carried, only the sides 76 b of the photoelectric transducerboard 76 are likely to contact the sides, i.e., the inner wall surfaces36 b, of the frame 36, and the corners 76 a of the photoelectrictransducer board 76 do not come into contact with or impinge on theframe 36. Even if some of the sides 76 b of the photoelectric transducerboard 76 are brought into contact with portions of the inner wallsurfaces 36 b of the frame 36, the photoelectric transducer board 76 issupported by two inner wall surfaces 36 b at a time, and hence theoverall weight of the photoelectric transducer board 76 is notconcentrated on one local region of the frame 36. Consequently, thephotoelectric transducer board 76 is free of risks of damage caused bythe sides, i.e., the inner wall surfaces 36 b, of the frame 36.

More specifically, according to the present embodiment, even if theradiation detecting apparatus 20 is dropped by mistake onto the floor,or is touched or hit by another object while the radiation detectingapparatus 20 is being carried, the photoelectric transducer board 76,e.g., the corners 76 a thereof, are prevented from becoming damaged andthe mechanical strength of the frame 36 of the casing 30 is maintained.Therefore, reliability of the radiation detecting apparatus 20 duringuse is increased.

Each of the recesses 200 is in the form of a cavity 202, which isconcave as viewed in plan. As indicated by the two-dot-and-dash lines inFIG. 4A, if the corresponding corner 76 a of the photoelectrictransducer board 76 were displaced toward the cavity 202 in order tobring two adjacent sides 76 b of the photoelectric transducer board 76into contact with respective inner wall surfaces 36 b of the frame 36 onboth sides of the cavity 202, the corner 76 a between the sides 76 bwould become spaced from the bottom of the cavity 202 by the minimumdistance da in the range from 1 mm to 5 mm. Even if the sides 76 b ofthe photoelectric transducer board 76 come into contact with the innerwall surfaces 36 b of the frame 36, a gap remains between the corner 76a of the photoelectric transducer board 76 and the cavity 202. Further,even if the corner 76 a of the photoelectric transducer board 76vibrates due to an impact that may occur if the radiation detectingapparatus 20 is dropped onto the floor or is touched or hit by anotherobject, the corner 76 a is not brought into contact with the bottomsurface 202 b and inner wall surface of the cavity 202, and hence thephotoelectric transducer board 76 is prevented from becoming damagedupon vibration thereof.

In particular, as shown in FIG. 2, the cavity 202 is defined between thefirst surface 202 c, which is disposed closer to the first plate 34, andthe second surface 202 d, which is disposed closer to the second plate40. The surface 76 c of the photoelectric transducer board 76, whichfaces toward the first plate 34 of the photoelectric transducer board76, is spaced from the first surface 202 c by the minimum distance d1,and the surface 76 d, which faces toward the second plate 40, is spacedfrom the second surface 202 d by the minimum distance d2. Each of theminimum distances d1, d2 is in the range from 1 mm to 5 mm. Even if thesides 76 b of the photoelectric transducer board 76 come into contactwith the inner wall surfaces 36 b of the frame 36, a gap remains betweenthe corner 76 a of the photoelectric transducer board 76 and the cavity202, i.e., the bottom surface 202 b of the cavity 202. In addition, agap remains between the surface 76 c of the photoelectric transducerboard 76, which faces the first plate 34, and the first surface 202 c. Agap also remains between the surface 76 d of the photoelectrictransducer board 76, which faces the second plate 40, and the secondsurface 202 d. Even if the corner 76 a of the photoelectric transducerboard 76 vibrates in directions across the plane of the photoelectrictransducer board 76, due to an impact that may occur if the radiationdetecting apparatus 20 is dropped onto the floor or is touched or hit byanother object, the corner 76 a is prevented from contacting the innerwall surfaces of the cavity 202, i.e., the bottom surface 202 b, thefirst surface 202 c, the second surface 202 d, etc., and thus thephotoelectric transducer board 76 is prevented from becoming damagedupon vibration thereof.

According to the present embodiment, the thickness ta of the first baseplate 62, the thickness tb of the photoelectric transducer board 76, thethickness tc of the scintillator 78, and the height ha of the cavity 202along the thickness direction of the photoelectric transducer board 76are related to each other by the inequality:tb<ha<(ta+tb+tc).

More specifically, the height ha of the cavity 202 is greater than thethickness tb of the photoelectric transducer board 76, but is smallerthan the sum of the thickness ta of the first base plate 62, thethickness tb of the photoelectric transducer board 76, and the thicknesstc of the scintillator 78. Because of the above thickness relationship,and also the gaps referred to above, if the photoelectric transducerboard 76 is displaced upon the radiation detecting apparatus 20 beingdropped onto the floor or touched or hit by another object, the corner76 a of the photoelectric transducer board 76 partially enters into thecavity 202, but is prevented from coming into contact or colliding withthe frame 36.

In particular, as shown in FIG. 3, the vertical or transverse length Laof the photoelectric transducer board 76 is greater than the vertical ortransverse length Lb of the scintillator 78, and the horizontal orlongitudinal length Lc of the photoelectric transducer board 76 isgreater than the horizontal or longitudinal length Ld of thescintillator 78. Therefore, even if the photoelectric transducer board76 is displaced together with the scintillator 78, which may occur ifthe radiation detecting apparatus 20 is dropped onto the floor or istouched or hit by another object, the scintillator 78 is prevented fromcoming into contact or colliding with the frame 36.

Furthermore, according to the present embodiment, as shown in FIG. 2,the first plate 34 and the first base plate 62 are secured to each otherby the first adhesive layer 64, and the first base plate 62 and thephotoelectric transducer board 76 are bonded to each other by adouble-sided pressure-sensitive adhesive tape. Since the first baseplate 62 and the photoelectric transducer board 76 are bonded to eachother by a double-sided pressure-sensitive adhesive tape, the radiationdetector 60 can easily be replaced or repaired. Such a structure makesit easy for the photoelectric transducer board 76 to move if theradiation detecting apparatus 20 is dropped onto the floor or is touchedor hit by another object. However, as described above, even if thephotoelectric transducer board 76 is displaced, the corner 76 a of thephotoelectric transducer board 76 partially enters into the cavity 202,but is prevented from contacting or colliding with the frame 36.Therefore, even though the above structure allows the radiation detector60 to easily be replaced or repaired, reliability of the radiationdetecting apparatus 20 during use is increased.

As described above, even if the radiation detecting apparatus 20according to the present embodiment is dropped onto the floor, or istouched or hit by another object while the radiation detecting apparatus20 is being carried, the photoelectric transducer board 76, e.g., thecorners 76 a thereof, are prevented from being damaged, and themechanical strength of the frame 36 of the casing 30 is maintained.Therefore, reliability of the radiation detecting apparatus 20 duringuse is increased.

According to the present embodiment, moreover, the second base plate 66on the rear side of the radiation detector 60 includes the first member118 and the second member 120, which have different functions,respectively. The first member 118 is made of a material for reducingthe weight of the radiation detector 60, whereas the second member 120is made of a metal material for attenuating scattered rays. Therefore,the second base plate 66 is effective to reduce the weight of theradiation detector 60 as well as to attenuate scattered rays applied tothe scintillator 78, thereby reducing noise images that are produced bysuch scattered rays.

The radiation detecting apparatus 20 does not require a single metalplate or a stacked assembly of metal plates made of different materialsdepending on the transmittance or scattering probability of radiation,but rather, the radiation detecting apparatus 20 comprises the secondbase plate 66 including the first member 118 and the second member 120.Therefore, the number of steps required to manufacture the radiationdetecting apparatus 20 is reduced, and the overall thickness of theradiation detecting apparatus 20 is not increased. Since a lead plate isnot included in the radiation detecting apparatus 20, the radiationdetecting apparatus 20 is reduced in weight. Since the second base plate66, which supports the radiation detector 60 and reinforces themechanical strength of the scintillator 78, doubles as a member forattenuating scattered rays, a dedicated base plate for attenuatingscattered rays is not required in the radiation detecting apparatus 20,so that the radiation detecting apparatus 20 can be made lower inprofile with a reduced thickness.

As described above, the radiation detecting apparatus 20 according tothe present embodiment is capable of reducing the adverse effects ofscattered rays, is reduced in weight, and is low in profile with areduced thickness.

The metal material of the second member 120 is the same as the metalmaterial of the electrically conductive patterns of the circuit boards56, which are disposed behind the second base plate 66. The metalmaterial of the second member 120 and the metal material of theelectrically conductive patterns of the circuit boards 56 are thuseffective to attenuate scattered rays applied to the scintillator 78.

In addition, the thickness of the second member 120 is changed dependingon the position of the circuit boards 56, so as to make noise imagesproduced by the attenuated scattered rays, which are applied to thescintillator 78, constant in level as a whole. In a case whereradiographic image information is generated by the radiation detectingapparatus 20, the noise levels are not easily noticed in theradiographic image information, and hence the image quality of an imagerepresented by the radiographic image information is prevented frombeing lowered by noise.

The present invention is not limited to the radiation detectingapparatus 20 according to the above embodiment, but various changes andmodifications may be made to the radiation detecting apparatus 20without departing from the essence of the invention.

FIGS. 10 and 11 show a modified radiation detector 600 according to amodification of the present invention. FIG. 10 is an enlargedcross-sectional view, partially omitted from illustration, of themodified radiation detector 600, and showing three pixel regionsthereof.

As shown in FIG. 10, the radiation detector 600 includes a plurality ofsignal output units 604, a plurality of sensors 606, and a scintillator608, which are disposed successively on an insulative substrate 602. Thesignal output units 604 and the sensors 606 make up respective pixels.The pixels are arrayed in rows and columns on the substrate 602, withthe signal output unit 604 and the sensor 606 being superposed one onthe other in each pixel.

The scintillator 608 is disposed over the sensors 606 with a transparentinsulating film 610 interposed therebetween. The scintillator 608includes a deposited layer of phosphor for converting radiation 12,which is applied downwardly in FIG. 10, into light, and emitting thelight. Emitted light from the scintillator 608 has a wavelength range,which is preferably a visible wavelength range from 360 nm to 830 nm. Ifthe radiation detector 600 is intended to capture monochromatic images,then the wavelength range of light emitted from the scintillator 608preferably includes a wavelength range of green light.

If the radiation 12 comprises X-rays, then the phosphor of thescintillator 608 should preferably include cesium iodide (CsI), and morepreferably, CsI(Tl) (thallium-doped cesium iodide), which emits light ina wavelength spectrum ranging from 420 nm to 700 nm upon beingirradiated with X-rays. The visible wavelength range of CsI(Tl) has apeak wavelength of 565 nm.

The scintillator 608 may be formed by evaporating columnar crystallineCsI(Tl) onto a base, for example. For forming the scintillator 608 byway of evaporation, the base onto which CsI(Tl) is to be evaporatedfrequently is made of aluminum, in view of facilitating X-raytransmittance and reducing costs. However, the material of the base isnot limited to aluminum. If the scintillator 608 is made of GOS, thenthe scintillator 608 may be formed by coating the surface of a TFTactive matrix substrate with GOS. Alternatively, the scintillator 608may be formed by coating a resin base with GOS, which is then bonded toa TFT active matrix substrate. The latter option is advantageous in thatthe TFT active matrix substrate can be saved in the event that the resinbase is not properly coated with GOS.

Each of the sensors 606 includes an upper electrode 612, a lowerelectrode 614, and a photoelectric transducer film 616 disposed betweenthe upper electrode 612 and the lower electrode 614.

Since the upper electrode 612 is required to apply light emitted fromthe scintillator 608 to the photoelectric transducer film 616, the upperelectrode 612 preferably is made of an electrically conductive material,which is transparent to at least the wavelength range of light emittedfrom the scintillator 608. More specifically, the upper electrode 612preferably is made of transparent conducting oxide (TCO), which has ahigh transmittance to visible light and a low resistance value. Althoughthe upper electrode 612 may be made of a thin film of metal such as goldor the like, the upper electrode 612 preferably is made of TCO, becausethe resistance value of gold is likely to increase if the transmittanceis increased to 90% or higher. Examples of TCO include ITO, IZO, AZO,FTO, SnO₂, TiO₂, ZnO₂, etc., of which ITO is most preferable from thestandpoint of process simplicity, low resistance, and transparency. Theupper electrode 612 may be a single electrode, which is shared by all ofthe pixels, or may be a plurality of separate electrodes belonging toeach of the respective pixels.

The photoelectric transducer film 616, which contains an organicphotoconductor (OPC), absorbs light emitted from the scintillator 708,and generates electric charges depending on the absorbed light. Thephotoelectric transducer film 616, which contains an organicphotoconductor (organic photoelectric transducer material), exhibits asharp absorption spectrum in the visible wavelength range, and does notabsorb electromagnetic waves other than light emitted from thescintillator 708. The sensors 606 are thus capable of effectivelyreducing noise, which would otherwise be generated if radiation 12 wereabsorbed by the photoelectric transducer film 616. The photoelectrictransducer film 616 may contain amorphous silicon rather than an organicphotoconductor. A photoelectric transducer film 616 that containsamorphous silicon exhibits a wide absorption spectrum for efficientlyabsorbing light emitted from the scintillator 708.

The organic photoconductor contained in the photoelectric transducerfilm 616 preferably has a peak wavelength for absorbing light, which isclose to the peak wavelength of light emitted from the scintillator 708,in order to absorb the light emitted from the scintillator 708 mostefficiently. The peak wavelength of light absorbed by the organicphotoconductor should ideally be the same as the peak wavelength oflight emitted from the scintillator 708. However, if the differencebetween such wavelengths is small enough, then the organicphotoconductor can sufficiently absorb light emitted from thescintillator 708. More specifically, the difference between the peakwavelength of light absorbed by the organic photoconductor and the peakwavelength of light emitted from the scintillator 708 preferably is 10nm or smaller, and more preferably, is 5 nm or smaller.

Examples of organic photoconductors that meet the above requirementsinclude quinacridone-based organic compounds and phthalocyanine-basedorganic compounds. Inasmuch as the peak wavelength of light in thevisible wavelength range, which is absorbed by quinacridone, is 560 nm,the organic photoconductor may be made of quinacridone and thescintillator 608 may be made of CsI(Tl), for thereby making it possibleto reduce the difference between the peak wavelengths to 5 nm orsmaller, and for substantially maximizing the amount of electric chargesgenerated by the photoelectric transducer film 616.

Each of the sensors 606 includes an organic layer formed by superposingor mixing a region for absorbing electromagnetic waves, a photoelectrictransducer region, an electron transport region, a hole transportregion, an electron blocking region, a hole blocking region, acrystallization preventing region, electrodes, and an interlayercontact-improving region. The organic layer preferably contains anorganic p-type compound (organic p-type semiconductor) or an organicn-type compound (organic n-type semiconductor).

The organic p-type semiconductor is a donor organic semiconductor(compound), mainly typified by a hole transport organic compound, andrefers to an organic compound that tends to donate electrons. Morespecifically, in a case where two organic materials are used in contactwith each other, one of the organic materials, which has a lowerionization potential, is referred to as a donor organic compound. Any ofvarious organic compounds, which are capable of donating electrons, canbe used as a donor organic compound.

The organic n-type semiconductor is an acceptor organic semiconductor(compound), mainly typified by an electron transport organic compound,and refers to an organic compound that tends to accept electrons. Morespecifically, in a case where two organic materials are used in contactwith each other, one of the organic materials, which has a largerelectron affinity, is referred to as an acceptor organic compound. Anyof various organic compounds, which are capable of accepting electrons,can be used as an acceptor organic compound.

Materials, which can be used as the organic p-type semiconductor and theorganic n-type semiconductor, and arrangements of the photoelectrictransducer film 616 are disclosed in detail in Japanese Laid-Open PatentPublication No. 2009-032854, and will not be described in detail below.The photoelectric transducer film 616 may contain fullerene or carbonnanotubes.

The thickness of the photoelectric transducer film 616 should preferablybe as large as possible, for thereby absorbing light from thescintillator 608. If the thickness of the photoelectric transducer film616 is greater than a certain value, then the electric field intensitygenerated on the photoelectric transducer film 616 by the bias voltageapplied from both ends of the photoelectric transducer film 616 isreduced, so that the photoelectric transducer film 616 cannot collectelectric charges. The thickness of the photoelectric transducer film 616preferably is in the range from 30 nm to 300 nm, more preferably, is inthe range from 50 nm to 250 nm, and even more preferably, is in therange from 80 nm to 200 nm.

The photoelectric transducer film 616 comprises a single photoelectrictransducer film, which is shared by all of the pixels, however, thephotoelectric transducer film 616 may also comprise a plurality ofseparate photoelectric transducer films belonging respectively to eachof the pixels. The lower electrode 614 comprises a plurality of separatelower electrodes belonging to the respective pixels, however, the lowerelectrode may also comprise a single lower electrode, which is shared byall of the pixels. The lower electrode 614 may be made of anelectrically conductive material, which is transparent or opaque, andpreferably is made of aluminum, silver, or the like. The lower electrode614 has a thickness in the range from 30 nm to 300 nm, for example.

In each of the sensors 606, a prescribed bias voltage is applied betweenthe upper electrode 612 and the lower electrode 614, so as to move onetype of electric charges, i.e., either electrons or holes, generated bythe photoelectric transducer film 616 to the upper electrode 612, and tomove the other type of electric charges to the lower electrode 614. Inthe modified radiation detector 600, the bias voltage is applied to theupper electrode 612 through a wire connected thereto. The bias voltagehas a polarity such that electrons generated by the photoelectrictransducer film 616 move to the upper electrode 612, and holes move tothe lower electrode 614. However, the bias voltage may be of an oppositepolarity.

The sensor 606 of each of the pixels may include at least the lowerelectrode 614, the photoelectric transducer film 616, and the upperelectrode 612. In order to prevent an increase in dark current, thesensor 606 preferably includes in addition at least one of an electronblocking film 618 and a hole blocking film 620, and more preferably,includes both of such films.

The electron blocking film 618 may be disposed between the lowerelectrode 614 and the photoelectric transducer film 616. The electronblocking film 618 is effective to prevent an increase in dark current,due to electrons being introduced from the lower electrode 614 into thephotoelectric transducer film 616 in a case where the bias voltage isapplied between the lower electrode 614 and the upper electrode 612.

The electron blocking film 618 may be made of an electron-donatingorganic material. Actually, the material of the electron blocking film618 may be selected depending on the material of the adjacent lowerelectrode 614 and the material of the adjacent photoelectric transducerfilm 616. The material of the electron blocking film 618 preferably hasan electron affinity (Ea), which is greater than the work function (Wf)of the material of the adjacent lower electrode 614 by 1.3 eV or higher,and preferably also has an ionization potential (Ip), which is equal toor smaller than the ionization potential of the material of the adjacentphotoelectric transducer film 616. Materials applicable as theelectron-releasing organic material are described in detail in JapaneseLaid-Open Patent Publication No. 2009-032854, and will not be describedbelow.

The electron blocking film 618 has a thickness preferably in the rangefrom 10 nm to 200 nm, more preferably, in the range from 30 nm to 150nm, and even more preferably, in the range from 50 nm to 100 nm, inorder to provide a reliable dark current preventing effect, and also toprevent the photoelectric transducing efficiency of the sensor 606 frombeing reduced.

The hole blocking film 620 is disposed between the photoelectrictransducer film 616 and the upper electrode 612. The hole blocking film620 is effective to prevent an increase in dark current, due toelectrons being introduced from the upper electrode 612 into thephotoelectric transducer film 616 in a case where the bias voltage isapplied between the lower electrode 614 and the upper electrode 612.

The hole blocking film 620 may be made of an electron-accepting organicmaterial. The hole blocking film 620 has a thickness preferably in therange from 10 nm to 200 nm, more preferably, in the range from 30 nm to150 nm, and even more preferably, in the range from 50 nm to 100 nm, inorder to provide a reliable dark current preventing effect, and also toprevent the photoelectric transducing efficiency of the sensor 606 frombeing reduced.

Actually, the material of the hole blocking film 620 may be selecteddepending on the material of the adjacent upper electrode 612 and thematerial of the adjacent photoelectric transducer film 616. The materialof the hole blocking film 620 preferably has an ionization potential(Ip), which is equal to or greater than the work function (Wf) of thematerial of the adjacent upper electrode 612 by 1.3 eV or higher, andpreferably also has an electron affinity (Ea), which is equal to orgreater than the electron affinity of the material of the adjacentphotoelectric transducer film 616. Materials applicable as theelectron-accepting organic material are described in detail in JapaneseLaid-Open Patent Publication No. 2009-032854, and will not be describedbelow.

For setting the bias voltage in order to cause holes generated in thephotoelectric transducer film 616 to move to the upper electrode 612,and also to cause electrons generated in the photoelectric transducerfilm 616 to move to the lower electrode 614, the electron blocking film618 and the hole blocking film 620 may be switched in position. It isnot necessary for the modified radiation detector 600 to have both theelectron blocking film 618 and the hole blocking film 620, but eitherone of such films may be included, to thereby provide a certain reliabledark current preventing effect.

As shown in FIG. 10, the signal output units 604 are disposed on thesurface of the substrate 602 in alignment respectively with the lowerelectrodes 614 of the pixels. Each of the signal output units 604 has astorage capacitor 622 for storing electric charges moved to the lowerelectrode 614, and a TFT 624 for converting electric charges stored inthe storage capacitor 622 into electric signals and outputting theelectric signals. The storage capacitor 622 and the TFT 624 are disposedin an area underlapping the lower electrode 614 as viewed in plan, sothat the signal output unit 604 and the sensor 606 of each pixel aresuperposed in the thickness direction of the modified radiation detector600. In the signal output unit 604, the lower electrode 614 fully coversthe storage capacitor 622, and the TFT 624 minimizes the surface area ofthe modified radiation detector 600 including the pixels thereof.

Each of the storage capacitors 622 is connected to a corresponding lowerelectrode 614 by an interconnecting structure, which is made of anelectrically conductive material that extends through an insulating film626 disposed between the substrate 602 and the lower electrode 614.Electric charges that are collected by the lower electrode 614 can bemoved to the storage capacitor 622 via the interconnecting structure.

As shown in FIG. 11, each of the TFTs 624 includes a gate electrode 628,a gate insulating film 630, and an active layer (channel layer) 632,which are stacked together, and a source electrode 634 and a drainelectrode 636 disposed on the active layer 632 and which are spaced fromeach other. The active layer 632 may be made of amorphous silicon, anamorphous oxide, an organic semiconductor material, carbon nanotubes, orthe like. However, the material of the active layer 632 is not limitedto such materials.

The amorphous oxide, which may be used for forming the active layer 632,preferably is an oxide, e.g., an In—O oxide containing at least one ofIn, Ga, and Zn, more preferably is an oxide, e.g., an In—Zn—O oxide, anIn—Ga—O oxide, or a Ga—Zn—O oxide containing at least two of In, Ga, andZn, or even more preferably, is an oxide containing In, Ga, and Zn. TheIn—Ga-An-O amorphous oxide preferably is an amorphous oxide having acrystalline state represented by InGaO₃(ZnO)_(m) (where m is a naturalnumber smaller than 6), or more preferably, InGaZnO₄. However, theamorphous oxide of the active layer 632 is not limited to the abovematerials.

The organic semiconductor material, which the active layer 632 may bemade of, may be, but should not be limited to, a phthalocyaninecompound, pentacene, vanadylphthalocyanine, or the like. Details of aphthalocyanine compound are described in Japanese Laid-Open PatentPublication No. 2009-212389, and will not be described below.

The active layer 632 of the TFT 624, which is made of amorphous oxide,an organic semiconductor material, or carbon nanotubes, does not absorbradiation 12 such as X-rays or the like, or only absorbs trace amountsof such radiation 12, thereby effectively preventing the signal outputunit 604 from producing noise.

If the active layer 632 is made of carbon nanotubes, then the switchingspeed of the TFT 624 is increased, and the TFT 624 has a low lightabsorption level in the visible wavelength range. If the active layer632 is fabricated of carbon nanotubes, and if even an extremely smallamount of metal impurity is introduced into the active layer 632, thecapability of the TFT 624 is greatly lowered. Therefore, it is necessaryto separate and extract highly pure carbon nanotubes by way ofcentrifugal separation or the like.

The amorphous oxide, the organic semiconductor material, the carbonnanotubes, and the organic photoconductor referred to above can be grownas a film at low temperatures. Therefore, the substrate 602 is notlimited to a heat-resistant substrate, such as a semiconductorsubstrate, a quartz substrate, or a glass substrate, but may be aflexible substrate of plastic or a substrate made of aramid orbionanofibers. More specifically, the substrate 602 may be a flexiblesubstrate of polyester, such as polyethylene terephthalate, polybutylenephthalate, polyethylene naphthalate, or the like, or polystyrene,polycarbonate, polyethersulfone, polyarylate, polyimide,polycycloolefine, norbornene resin, polychlorotrifluoroethylene, or thelike. Such a flexible substrate of plastic makes the modified radiationdetector 600 lighter in weight and hence easier to carry.

The photoelectric transducer film 616 may be made of an organicphotoconductor, and the TFT 624 may be made of an organic semiconductormaterial, which can be grown on a flexible plastic substrate, i.e., thesubstrate 602, at low temperatures, whereby the modified radiationdetector 600 can be reduced in thickness and weight as a whole. Theradiation detecting apparatus 20, which incorporates the radiationdetector 600 therein, can also be reduced in thickness and weight,thereby making the radiation detecting apparatus 20 convenient for useoutside of a hospital or the like. Since the substrate 602, which servesas a base member for the photoelectric transducer, is made of a flexiblematerial rather than glass, the radiation detector 600 is resistant todamage when the radiation detecting apparatus 20 is carried.

The substrate 602 may include an insulative layer for making thesubstrate 602 insulative, a gas barrier layer for making the substrate602 impermeable to water and oxygen, and an undercoat layer forincreasing the flatness of the substrate 602, thereby making thesubstrate 602 capable of closely contacting electrodes.

Aramid is advantageous in that, since a high-temperature process at 200degrees Celsius is applicable thereto, aramid allows a transparentelectrode material to be set at a high temperature for achieving lowerresistance. Aramid also allows driver ICs to be automatically mountedthereon by a process including a solder reflow process. Furthermore,inasmuch as aramid has a coefficient of thermal expansion close to thatof ITO (Indium Tin Oxide) and glass, a substrate 602 made of aramid isless liable to become warped or cracked after fabrication. In addition,a substrate 602 of aramid may be made thinner than a glass substrate orthe like. The substrate 602 may be in the form of a stacked assembly ofan ultrathin glass substrate and an aramid film.

Bionanofibers are made by compounding a bundle of cellulose microfibrils(bacteria cellulose) produced by bacteria (acetic acid bacteria,Acetobacter Xylinum) and a transparent resin. The bundle of cellulosemicrofibrils has a width of 50 nm, which is 1/10 of the wavelength ofvisible light, is highly strong and highly resilient, and is subject tolow thermal expansion. Bionanofibers, which contain 60% to 70% of fibersand exhibit a light transmittance of approximately 90% at a wavelengthof 500 nm, can be produced by impregnating bacteria cellulose with atransparent resin such as an acrylic resin, an epoxy resin, or the like,and then setting the transparent resin. Bionanofibers are flexible, andhave a low coefficient of thermal expansion ranging from 3 ppm to 7 ppm,which is comparable to silicon crystals, a high strength of 460 MPa thatmatches the strength of steel, and a high resiliency of 30 GPa.Therefore, a substrate 602 made of bionanofibers can be thinner thanglass substrates or the like.

According to the present modification, the signal output units 604, thesensors 606, and the transparent insulating film 610 are successivelydisposed on the substrate 602, and the scintillator 608 is bonded to thetransparent insulating film 610 by an adhesive resin of low lightabsorption, thereby producing the radiation detector 600.

Since the photoelectric transducer film 616 is made of an organicphotoconductor, and the active layer 632 of each TFT 624 is made of anorganic semiconductor material, the photoelectric transducer film 616and the signal output units 604 essentially do not absorb radiation 12.Consequently, the sensitivity of the modified radiation detector 600 isprevented from being lowered.

The organic semiconductor material of the active layer 632 of each TFT624, and the organic photoconductor of the photoelectric transducer film616 can be grown as a film at low temperatures. Therefore, the substrate602 may be made of plastics, aramid, or bionanofibers, in order tofurther prevent the sensitivity of the modified radiation detector 600from being lowered.

If the modified radiation detector 600 is bonded to the irradiatedsurface 32 in the casing, and the substrate 602 is made of highly rigidplastics, aramid, or bionanofibers, then since the rigidity of theradiation detector 600 is increased, the portion of the casing aroundthe irradiated surface 32 can be made thin. If the substrate 602 is madeof highly rigid plastics, aramid, or bionanofibers, then since theradiation detector 600 is flexible, the radiation detector 600 is lessliable to be damaged in a case where shocks are applied to theirradiated surface 32.

The modified radiation detector 600 is of a PSS (Penetration SideSampling) type as a reverse-side readout type, wherein the sensors 606(the photoelectric transducer film 616), which are positioned behind thescintillator 608 remotely from the radiation source 16, convert lightemitted from the scintillator 608 into electric charges in order to readradiographic image information. However, the modified radiation detector600 is not limited to a PSS type.

The modified radiation detector 600 may be a face-side readout ISS(Irradiation Side Sampling) type of radiation detector, in which thesubstrate 602, the signal output units 604, the sensors 606, and thescintillator 608 are arranged successively along the direction in whichradiation 12 is applied, and the sensors 606, which are positioned infront of the scintillator 608 proximate the radiation source 16, convertlight emitted from the scintillator 608 into electric charges in orderto read radiographic image information. In accordance with such an ISStype radiation detector, inasmuch as light emitted from the scintillator608 is prevented from being scattered and attenuated before the light isdetected by the sensors 606, the generated radiographic imageinformation is of high resolution.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made to the embodiments withoutdeparting from the scope of the invention as set forth in the appendedclaims.

What is claimed is:
 1. A radiation detecting apparatus comprising: aradiation detector including a scintillator configured to convertradiation that has passed through a subject into visible light, and asubstantially rectangular shaped photoelectric transducer boardconfigured to convert the visible light into radiographic imageinformation; and a casing housing the radiation detector therein,wherein the casing is of a substantially rectangular shape and includesan upper plate, a lower plate, and a side plate interconnecting theupper plate and the lower plate; the side plate has a recess definedtherein, which faces and is spaced from a corner of the photoelectrictransducer board, the recess being concave in a direction away from thecorner; the corner of the photoelectric transducer board has a chamferin an area that faces the recess; the recess comprises a cavity, whichis concave as viewed in plan; the cavity includes two side wall surfacesconfigured to adjoin the respective inner wall surfaces, and a bottomsurface configured to interconnect the two side wall surfaces; thechamfer of the corner of the photoelectric transducer board includes twoapexes as viewed in plan; and a space is present between the chamfer andthe bottom surface of the cavity, the chamfer and the bottom surface ofthe cavity facing each other and substantially parallel to each other.2. The radiation detecting apparatus according to claim 1, wherein oneof the two apexes that is closest to the bottom surface is spaced fromthe bottom surface of the cavity by a minimum distance of a range from 1mm to 5 mm.
 3. The radiation detecting apparatus according to claim 2,wherein the recess comprises a cavity, which is concave as viewed inplan, and which is concave as viewed in vertical cross section; thecavity is defined between a first surface, which is closer to the upperplate, and a second surface, which is closer to the lower plate; thephotoelectric transducer board has a surface facing the upper plate andspaced from the first surface by a minimum distance, and a surfacefacing the lower plate and spaced from the second surface by a minimumdistance, each of the minimum distances being in the range from 1 mm to5 mm.
 4. The radiation detecting apparatus according to claim 3, furthercomprising: a first base plate disposed between the upper plate and thephotoelectric transducer board and supporting the radiation detectorthereon; the scintillator is disposed on a surface of the photoelectrictransducer board, which is remote from the first base plate; and thefirst base plate has a thickness ta, the photoelectric transducer boardhas a thickness tb, the scintillator has a thickness tc, and the cavityhas a height ha along a thickness direction of the photoelectrictransducer board, the thicknesses ta, tb, tc and the height ha beingrelated to each other by the inequality tb <ha <(ta +tb +tc).
 5. Theradiation detecting apparatus according to claim 4, wherein thephotoelectric transducer board has a transverse length greater than atransverse length of the scintillator, and a longitudinal length greaterthan a longitudinal length of the scintillator.
 6. The radiationdetecting apparatus according to claim 4, wherein the upper plate andthe first base plate are fixed to each other by an adhesive layer; andthe first base plate and the photoelectric transducer board are bondedto each other by a pressure-sensitive adhesive.
 7. The radiationdetecting apparatus according to claim 4, further comprising: a secondbase plate disposed between the scintillator and the lower plate, andwhich supports the radiation detector thereon in coaction with the firstbase plate; the upper plate and the first base plate are fixed to eachother by an adhesive layer; the first base plate and the photoelectrictransducer board are bonded to each other by a pressure-sensitiveadhesive; and the second base plate and the scintillator are bonded toeach other by a pressure-sensitive adhesive.
 8. The radiation detectingapparatus according to claim 7, wherein the first base plate is made ofa non-metal material; and the second base plate is made principally of anon-metal material.